Myotube production in fast myotomal muscle is switched‐off at shorter body lengths in male than female Atlantic halibutHippoglossus hippoglossus(L.) resulting in a lower final fibre number

Abstract

A sampling method is described to determine accurately the number of fast myotomal muscle fibres (N F ) in a large flatfish species, the Atlantic halibut Hippoglossus hippoglossus. An unusual feature of the fast myotomal muscle is the presence of internalized strips of slow muscle fibres. In fish of 1Á5-3Á5 kg (n ¼ 24), the total cross-sectional area (A TC ) of fast muscle was 18% greater in the dorsal than ventral myotomal compartments (P < 0Á05), whereas there was no significant difference between left-and right-hand sides of the body. Due the bilateral asymmetry, muscle blocks (5 Â 5 Â 5 mm) were prepared to systematically sample each myotomal quadrant (dorsal, ventral, left-and right-side) and the diameters of 150 fast fibres measured per block. Smooth non-parametric probability functions were fitted to a minimum of 800 measurements of fibre diameter per quadrant (n ¼ 5). There were no significant differences in the distribution of muscle fibre diameters between myotomal compartments and therefore N F could be estimated from a single quadrant. The number of blocks required to estimate N F with a repeatability of AE2Á5% increased from six at 300 g body mass to 17 at 96Á5 kg, caused by variation within and between blocks. Gompertz curves were fitted to measurements of fibre number and fork length (L F ). The estimated final fibre number was 8Á96 Â 10 5 (7Á99-9Á94 Â 10 5 , 95% CI) for males and 1Á73 Â 10 6 (1Á56-1Á90 Â 10 6 , 95% CI) for female fish. The estimated L F for cessation of fibre recruitment in the fast muscle of female fish (1775 mm) was almost twice that in males (810 mm), reflecting their greater ultimate body size.

Study of Some Histological Properties of Skeletal Muscles in a Fish Gymnura micrura

“…It is noted that the type of fish studied has a larger white muscle fiber compared to red muscle fibers. This reflects the nature of the movement and nutrition of the fish, which is characterized by slow motion and carnivores, in addition to possessing a large proportion of the cartilage skeletal of different types, which function as a reference to the movement of the body in the water environment and this is what the results of the current study of tissue sections [8,17,18]. [19], pointed out that the fish that spend most of the time in swimming characterized by a high proportion of red muscles in addition to the presence of deep red muscles located in the muscular tissue in the muscular tissue, indicating that it is a movement of continuous and for a long time.…”

Interactive effect of photoperiod and temperature on the growth rates, muscle growth and feed intake in juvenile Atlantic halibut

“…Further, an optimal fibre hypothesis has been proposed suggesting that there is a trade‐off between requirements to avoid diffusional constraints while maximizing fibre diameter to minimize the energy costs of ionic homeostasis (Johnston, Fernandez et al 2003; Johnston 2006). Lower surface to volume ratio in muscle fibres results in a reduced passive leak of ions across the muscle membrane and hence the cost of pumping ions to maintain ionic homeostasis is reduced (Johnston 2006; Hagen et al 2008).…”

“…In conclusion, continuous light had a growth‐promoting effect only at a low temperature, indicating an inverse relation between temperature and photoperiod. Alterations in the timing of onset of continuous light relative to season may induce other subtle differences, interacting with size and stage and overlaying a seasonal cycle of myotube formation until about 80 cm TL in male Atlantic halibut (Hagen et al 2008). Nonetheless, reductions in routine maintenance costs by continuous light may allow earlier development of larger fibre diameters and thus better growth in small juvenile halibut, even in cold water.…”

“…Significantly trunk muscle fibres are helically arranged within W‐shaped myotomes separated by thin layers of collagen (myosepts), forming angles up to 40° from the body axis of the fish (Bone 1978). Furthermore, adult halibut have internal bands of slow (red) muscle fibres nested within the fast trunk muscles (Hagen, Vieira, Solberg & Johnston 2008) but the ontogeny of these is unclear. These points have important implications for the sampling and replicability of diameter and number of muscle fibres in halibut.…”

The TORC1/P70S6K and TORC1/4EBP1 signaling pathways have a stronger contribution on skeletal muscle growth than MAPK/ERK in an early vertebrate: Differential involvement of the IGF system and atrogenes

“…Body weight was obtained by weighing the whole fish. For muscle cellularity assessment, a 0.5 cm steak was obtained and the number of blocks (0.5 Â 0.5 cm) was estimated according to Hagen et al (2008). Blocks were obtained from both the dorsal and ventral positions, fixed with Shandon Glyo-Fixx (Thermo Scientific, IL, USA) for 24 h at 4°C, dehydrated with ethanol gradients (80-90-95-95-100-100-100% for 10 min in each alcohol concentration) and xylol (100% for 10 min, 3 times), and embedded in paraffin (Paraplast plus, McCormick Scientific, MO, USA).…”